PubMed^® Literature Review

The posterior bundle of the medial collateral ligament (pMCL) plays a significant role in maintaining elbow stability, particularly against valgus stress and posteromedial rotatory instability (PMRI) [1][7]. PMRI is characterized by a specific pattern of osseous and soft tissue injuries that include anteromedial coronoid fractures with associated lateral collateral ligament complex (LCLC) injury [2]. It has been established that the integrity of the pMCL is essential for preventing PMRI as it resists valgus torque at various flexion angles [7]. Biomechanical analyses have demonstrated that isolated sectioning of the anterior bundle does not lead to complete dislocation until the pMCL is also compromised [7]. This suggests that while both bundles contribute to elbow stability, the pMCL serves as an important restraint against posterior dislocation across all flexion angles. Consequently, reconstruction techniques have evolved to address both anterior and posterior bundles when treating MCL injuries associated with instability or dislocation [7]. The relationship between contact pressures within the elbow joint structures during varus stress has been explored through biomechanical testing using cadaveric models. These studies reveal that intact specimens exhibit lower mean contact pressures compared to those with simulated PMRI injuries involving both LCLC tears and anteromedial subtype coronoid fractures combined with pMCL tears [1][8]. Notably, even without subluxation or joint incongruity caused by LCL lesions alone, increased contact pressures are observed in elbows affected only by anteromedial subtype coronoid fracture combined with pMCL tear compared to intact specimens [1]. Elbow stabilizers consist not only of ligamentous structures but also muscular components such as flexor-pronator muscles which actively contribute to valgus stability alongside passive stabilizers like MUCL[9]. Mechanoreceptors present within these ligaments suggest their role extends beyond mere mechanical support; they may provide proprioceptive feedback crucial for dynamic stabilization during movement[6]. In addressing failed lateral collateral ligament reconstructions – which often result in PMRI – preoperative risk factors concerning bony anatomy or soft tissue constraints must be considered along with operative factors such as tunnel placement or graft positioning[4]. Understanding these risk factors can inform preventative strategies. The interplay between different components contributing to elbow stability underscores a complex system where each element cannot be viewed in isolation. For instance, recent findings indicate that even parts typically not recognized as primary stabilizers – like the lateral part of distal triceps – play significant roles under certain conditions such as LCL-deficient elbows[8]. In summary, based on current literature spanning over two decades up till 2023[10], it's evident that while multiple elements contribute towards overall elbow stability against forces leading to PMRI including muscle loading effects from anconeus or triceps muscles[8], it's clear that preserving or restoring integrity specifically targeting pMCl remains paramount due its pivotal function against varus torque-induced instabilities across varying degrees elbow flexion.